Field of the Invention
The present invention relates to a structure.
Discussion of the Background
It is desired that, in heating furnaces used for growing crystals and the like at a high temperature, a time for raising the temperature to a predetermined processing temperature be short in order to shorten the processing time, while it is also desired that the temperature in the furnace should not rise excessively over the processing temperature after the temperature has reached the predetermined processing temperature, in order to make the heat treatment temperature stable.
For example, when growing an InGaSb crystal, a lump of GaSb material is placed in a heating furnace and an InGaSb material is placed thereon, and the heating furnace is inductively heated so that the temperature in the heating furnace is held between the melting point of GaSb (712° C.) and the melting point of InGaSb (in the range of 525° C. to 712° C.). When heating is carried out in this manner, only the InGaSb material melts to form an InGaSb crystal solution, which accumulates on top of the GaSb lump. Therefore, an InGaSb monocrystal can be grown by bringing a GaSb seed crystal into contact with this solution and pulling it up while rotating it, maintaining constant temperature of the InGaSb solution.
In the above mentioned process, it is desirable that the time for raising the temperature in the heating furnace to 525° C. or higher be short, while the temperature of the furnace should not exceed 712° C.
On this condition, in order to shorten the time for raising the temperature, it is effective to improve the heat insulating property inside the furnace in a low temperature region, thus, it is considered to be desirable to fabricate the furnace body (inner wall of the furnace) from a material having excellent heat insulating property, namely, a material having a low thermal conductivity.
Further, in order to prevent excessive rising of the temperature in the furnace exceeding the processing temperature, it is effective to enhance the heat releasing property in a high temperature region so that the temperature of the furnace body cannot easily rise in a high temperature region. Therefore, it is considered to be desirable to fabricate a furnace body from a material having excellent heat releasing property, namely, a material having a high emissivity.
Here, JP-A 2-47555 discloses a far infrared radiator comprises an inorganic compound coating film formed of oxide based ceramics and high-expansion glass with a low melting point on the surface of a metal base, as a material having excellent heat releasing property.
Further, JP-A 3-62798 discloses an infrared radiator comprises a high-infrared radiation coating film (black color at room temperature) formed of metal oxide and high-expansion glass with a low melting point on the surface of a metal base, as a material having similarly excellent heat releasing property.
The contents of JP-A 2-47555, JP-A 3-62798 are incorporated herein by reference in their entirety.